Making plate workpiece with regions of different thickness

ABSTRACT

A method of making a part with regions of different thickness from a plate workplace having a pair of substantially parallel plate faces. The workpiece is fitted between a surface of a die and a substantially parallel surface of a punch. The die is formed at its surface with an opening. Then the die and the punch are relatively shifted parallel to the surfaces and faces and so as to compress the workpiece parallel to its faces to extrude the workpiece transversely into the opening in the die surface, thereby creating a region of greater thickness.

FIELD OF THE INVENTION

[0001] The present invention relates to the manufacture of a plateworkpiece with regions of different thickness. More particularly thisinvention concerns a method of and apparatus for making a motor vehiclepart regions of reduced thickness so as to reduce weight and regions ofconsiderable thickness for strength.

BACKGROUND OF THE INVENTION

[0002] In the production of various construction elements, for instancethe A-, B-, and C-columns in a motor vehicle as well as in shockabsorbers and their support struts, roof beams, side frame elements, andspring arms it is often desirable for the element to have regions ofdifferent thickness. The thicker regions provide strength where neededwhile the thinner regions make the part as light as possible.

[0003] At one time this was most simply accomplished by laminatingtogether metal plates as so-called tailored blanks. Such construction isdifficult and delamination is always a problem leading to failure of thepart.

[0004] Accordingly German 4,231,213 of R. Hansen et al proposes makingthe part from a flat plate having a starting thickness equal to thethickest part of the finished workpiece. The thick plate is deformed andmachined so that its thickness is reduced everywhere except where itneeds to be thick. Such a system is difficult because the thin regionsof often account for most of the area of the workpiece, so the workreducing all this area to the desired thickness is considerable.

[0005] In another system described in German 100 63 040 of H. Knaup acar part is made by compressing a workpiece to form a bump in it, thenthe workpiece is machined at the bumps to reduce its thickness. Such asystem uses a great deal of material, in act reducing much of theworkpiece to chips or powder. In addition it requires multiple steps,deforming and machining for instance, to create the desired end product.It is extremely inefficient for the production of a workpiece only asmall portion of which needs to be thick.

OBJECTS OF THE INVENTION

[0006] It is therefore an object of the present invention to provide animproved method and apparatus for making a workpiece with regions ofdifferent thickness.

[0007] Another object is the provision of such an improved method andapparatus for making a workpiece with regions of different thicknesswhich overcome the above-given disadvantages, that is which is a simpleone-step operation that wastes little or none of the material of thestarting blank.

SUMMARY OF THE INVENTION

[0008] A method of making a part with regions of different thicknessfrom a plate workplace having a pair of substantially parallel platefaces. According to the invention the workpiece is fitted between asurface of a die and a substantially parallel surface of a punch. Thedie is formed at its surface with an opening. Then the die and the punchare relatively shifted parallel to the surfaces and faces and so as tocompress the workpiece parallel to its faces to extrude the workpiecetransversely into the opening in the die surface, thereby creating aregion of greater thickness. Normally the punch is moved relative to thedie, although it is within the scope of the invention to hold the punchstationary and move the die, or move both the punch and the die.

[0009] Thus with the system of this invention, rather than reducing theworkpiece thickness where the finished part is supposed to be thin, thethickness in increased where it needs to be thick. Since normally a parthas to be thick in a few locations, the inventive method issubstantially simpler and easier than the prior-art methods. No materialis lost from the workplace, so it is very efficient in this regard. Thedie can have several openings so that the workplace is thickened inseveral locations, but in any case the workpiece has a startingthickness that in the same as the thinnest regions of the finished part.The finished part can have, for instance, a thickened annular edge andone or more thickened regions forming stiffening ribs extending acrossit. A flange can be formed on one part of a workpiece. It is possible toproduce a finished part of a shape that could not be made by standardthrough-die extrusion or rolling.

[0010] The plate faces are in full surface contact with the die andpunch surfaces except at the opening. In addition the die surface issmother than the punch surface so that the workplace sticks to the punchand slides on the die because the coefficient of friction between theplate and the die is less than that between the plate and the punch.

[0011] The plate can be thickened according to the invention immediatelyafter being cut. Thus it passes directly from an automatic plate cuttingmachine to a thickening apparatus carrying out the method of thisinvention.

[0012] It is further possible according to the invention to heat theplate workpiece before fitting it to the die and punch. This can be doneby providing a heater right in the die and/or punch. Alternately theworkpiece can be heated in an oven and then immediately subjected to thecompression/thickening step of this invention. Hardening can take rightin the thickening apparatus so the finished part has an exactlydetermined shape.

[0013] The part according to the invention is very strong since thecrystalline structure of the metal, normally steel or aluminum, iscontinuous at the margins of the thickened regions. In fact the grainstructure has a shape conforming to the exterior surface, not the brokenone produced by machining away the workpiece at the thin regions. As aresult when the part is used in a motor vehicle it has excellent crashresistance, that is will retain strength even in an accident when it isseverely stressed.

BRIEF DESCRIPTION OF THE DRAWING

[0014] The above and other objects, features, and advantages will becomemore readily apparent from the following description, reference beingmade to the accompanying drawing in which:

[0015]FIGS. 1 and 2 are schematic sectional views illustrating themethod and apparatus of this invention before and after shaping aworkpiece;

[0016]FIG. 3 is a perspective view of a finished workpiece according tothe invention;

[0017]FIGS. 4 and 5 are cross sections taken along lines IV-IV and V-Vof FIG. 3;

[0018]FIG. 6 is a large-scale section through a prior-art weld joint;and

[0019]FIG. 7 is a view like FIG. 6 but using a workpiece according tothe invention.

SPECIFIC DESCRIPTION

[0020] As seen in FIGS. 1 and 2 a plate workpiece 1 is held in anforming apparatus 2 comprised of a stationary die 3 formed with asquare-section cavity 5 in which a punch 4 can slide in paralleldirections P₁ and P₂. One planar interior surface 16 of the cavity 5 isset back and forms a shoulder 6 directed backward in the direction P₂and a confronting planar surface 15 of the punch 5 is cut back to form ashoulder 7 confronting the shoulder 6. The punch 4 fits complementarilyin the cavity 5 and is only spaced from it at the surfaces 15 and 16between the shoulders 6 and 7 in a rectangular region having a constantdepth d₁ measured transverse to the directions P₁ and P₂ equal to thethickness of a plate-shaped metal blank 1.

[0021] The shoulders 6 and 7 are planar and can be perpendicular to thedirections P₁ and P₂ but preferably are canted at a slight angle theretoso that they converge outward away from the punch 4. The punch surface15 is roughened to increase friction forward, that is downward in thedrawing from the shoulder 7 but the confronting surface 16 of the cavity5 upward of the shoulder 6 is machined smooth.

[0022] In addition the die 3 is provided with an abutment 10 having aplanar face exposed in the cavity 5 and displaceable perpendicular tothe directions P₁ and P₂ in a passage 9 away from the cavity 5 againstthe force of a powerful compression spring 11. A pressurized hydraulicfluid could replace the spring 11. A stop or spacer 14 is provided inthe die 13 for engagement with a rear face 13 of the abutment 10 tolimit its movement away from the cavity 5.

[0023] In use the punch 4 is pulled completely out of the die 3. Thenthe punch 4 is fitted to the cavity 5 with its shoulder spaced retractedfar enough to space its shoulder 7 outside the die 3 by a distance equalto at least a length or height k of the plate 1 measured parallel to itsplane. The punch 4 is pushed downward in the direction P₁ until theleading edge of the plate 1 engages the shoulder 6. Further forceapplied in the direction P₁ will longitudinally compress the plate 1into a workpiece 1 a which deforms outward into the passage 15, pressingback the abutment 10 against the force of its spring 11 until it seatsagainst the stop 14. During thin compression, which is appliedlongitudinally and causes the workpiece to extrude transversely, theback face of the workpiece plate 1 is in full surface contact with therough face 15 of the punch 4. This forms a bump 12 on the workpiece 1 ahaving a shape corresponding to that of the passage 15, the bump 12having a planar end face like the end of the abutment 10. The finishedworkpiece has a height h₂ that is less than the height h₁. The Slightcanting of the two edges or shoulders 6 and 7, the roughness of thepunch surface 15, and the smoothness of the surface 16 ensure that theworkpiece 1 will slide along the die 3 and lie flat against the punch 4.

[0024]FIGS. 3, 4, and 5 show how this system can be applied to aworkpiece 17 to provided it with central thickened regions 18. Thesethickenings increase strength at critical corner and edge regions, whilethe rest of the workplace 17 is left thin so that it is quite light.

[0025]FIG. 6 shows how in the prior art two plates 19 and 20 are weldedtogether at 21. This action erodes the plates 19 and 20 at 22 reducingplate thickness S and thereby weakening the plate 19 locally.

[0026] According to the invention a similar weld at 25 between twoplates 24 is effected where the plate 23 has been thickened so that nothickness is lost.

I claim:
 1. A method of making a part with regions of differentthickness from a plate workpiece having a pair of substantially parallelplate faces, the method comprising the steps of: fitting the workpiecebetween a surface of a die and a substantially parallel surface of apunch, the die being formed at its surface with an opening; relativelyshifting the die and the punch parallel to the surfaces and faces andthereby compressing the workpiece to extrude the workpiece into theopening in the die surface while bracing the workpiece against the punchsurface.
 2. The method defined in claim 1 wherein the workpiece iscompressed edgewise parallel to its faces between the die and the punch.3. The method defined in claim 1 wherein the plate faces are in fullsurface contact with the die and punch surfaces except at the opening,the die and punch having confronting shoulders bearing on edges of theworkpiece.
 4. The method defined in claim 1 wherein the die surface issmoother than the punch surface, whereby the workpiece sticks to thepunch and slides on the die.
 5. The method defined in claim 1 whereinthe die is formed with a plurality of the openings, whereby theworkpiece is thickened at each of the openings.
 6. The method defined inclaim 1, further comprising the step of heating the plate workplacebefore fitting it to the die and punch.
 7. The method defined in claim 6wherein the workpiece is heated while fitted to the die and punch aftercompression.
 8. The apparatus defined in claim 1 wherein the plateworkpiece is of metal.
 9. The apparatus defined in claim 8 wherein themetal is aluminum or steel.
 10. An apparatus for of making a part withregions of different thickness from a plate workplace having a pair ofsubstantially parallel plate faces, the apparatus comprising: a diehaving a generally planar die surface and formed at the surface with anopening; a punch having a generally planar punch surface parallel to andspaced from the die surface, the workplace being fittable between thesurfaces with its faces in full surface contact with the surfaces; meansfor relatively shifting the punch and die relative to each otherparallel to the punch and die surfaces and thereby compressing theworkpiece to extrude the workpiece into the opening in the die surfacewhile bracing the workpiece in surface contact against the die surface.11. The apparatus defined in claim 10 wherein the punch and die haveshoulders projecting generally perpendicular to the respective surfacesand engageable with edges of the plate workpiece.
 12. The apparatusdefined in claim 11 wherein the die surface is smoother than the punchsurface.
 13. The apparatus defined in claim 10 wherein the die and punchsurfaces are spaced apart by a distance equal substantially to athickness of the plate workpiece.
 14. The apparatus defined in claim 10,further comprising: an abutment shiftable in the die transversely to thesurfaces in the opening and having an end face movable between anadvance position generally flush with the die surface and a retractedposition offset back from the die surface; and means for urging theabutment into the flush position.
 15. The apparatus defined in claim 14wherein the urging means is a spring.